The present invention relates to an envelope control apparatus suitable for producing a mandolin effect in an electronic musical instrument.
In a conventional apparatus for digitally producing a mandolin effect, an envelope counter for generating envelope data is operated when a player depresses a key. When the envelope counter completes counting one period of the envelope, the envelope counter is reset and starts counting again. This count operation is repeated a plurality of times until the player releases the key. As a result, the mandolin effect envelope waveform for a plurality of periods is produced. Therefore, the period of mandolin tone depends on the count cycle of the envelope counter. Unless the period of clock signals supplied to the envelope counter changes, a mandolin effect having an arbitrary period cannot be obtained. As a result, the produced tones become monotonous.
A plurality of apparatus for generating mandolin tones are arranged in an electronic musical instrument for generating a plurality of notes in a time divisional fashion. In this case, different mandolin effects are given to a plurality of notes which are simultaneously produced. Each mandolin effect is obtained by a corresponding one of envelopes having different periods. Therefore, beat noise occurs due to a frequency difference between the envelope waveforms, thus producing poor, uncomfortable sounds.